1. Field of the Invention
The present invention relates generally to a network system obtained by combining a wireless communication system and a cable communication system and a method of making a network, and more particularly to a network system having an access network dynamically made for a short-distance wireless communication and a method of making the access network.
2. Description of Related Art
Portable personal computers, portable information units such as personal digital assistants and internets have spread, and internet connection service through a portable telephone has rapidly spread. Therefore, the demand of wireless data communication service has been increased. In a portable telephone system of the third generation, high speed communication service is performed at a maximum of 2 M bit/sec (Mbps).
However, in contrast to the rapid increase of the demand of the data communication service, the frequency source is limited. Therefore, a method for performing communication at higher efficiency has been desired. In particular, it is afraid that the demand of the data communication service exceeds communication capacity in the peripheries of stations of urban areas.
To heighten the communication capacity, a higher frequency band is used, and micro wave communication in one frequency band is simultaneously performed in many areas by suppressing the output power of radio wave in each area. In particular, it is effective that many wireless communication systems respectively using the micro wave of a low output power are installed in the urban area.
In the current market of the communication system using the micro wave of a low output power, a wireless local area network (LAN) regulated in the Institute of Electrical and Electronic Engineers, Inc. (IEEE) 802.11 has been developed. Also, Bluetooth (registered trademark) have spread to connect information units with each other. The Bluetooth has been developed in place of the technique of infrared connection developed in the Infrared Data Association (IrDA). In the Bluetooth, a frequency band called an Industrial, Scientific and Medical (ISM) band is used because the band can be used for industrial, scientific and medical fields without license, and the output power is suppressed so as to perform a short-distance communication in a communication system at a maximum of 10 to 100 m distance. Therefore, a second communication system can use the same frequency band as that used in the communication system when the second communication system is placed far away from the communication system by the maximum distance or more.
Also, the communication environment of the cable internet connection has been developed to perform the communication at high speed. For example, a technique of DSL (digital subscriber line), cable modem or FTTH (fiber to the home) is used, and the internet connection service performed at a high communication speed of 1 Mbps to 100 Mbps can be used at a low charge such as thousands yen (or tens dollars) per month.
Therefore, it is expected that the wireless data communication service is performed in a private network or a small-sized area by combining the wireless communication system simply performed at a low output power and the cable communication system using the internet connection. For example, in a rail station or a cafe, the cable communication system using the internet connection of a high speed communication is set up, a wireless station is connected with the cable communication system, and the wireless data communication service is performed.
However, in cases where a plurality of wireless stations are disposed to provide the wireless data communication service for many users in a wide service area, it is required to connect cables with the wireless stations at many points in the wireless communication system. Also, it is required to connect a cable with a wireless station each time the wireless station is moved or added. Also, it is required to disconnect a cable from a wireless station each time the wireless station is removed. Therefore, it is troublesome to perform the cable connection with the wireless communication system at many points.
Because a conventional network system has the above-described configuration, a problem has arisen that it is difficult to add or move a wireless station.
In the specification of Published Unexamined Japanese Patent Application No. H8-37535, a technique of making an ad-hoc network is disclosed. In this ad-hoc network, a network is made by a plurality of wireless terminal units not respectively placed in a specific network. Also, the management of a communication route between each pair of mobile wireless terminal units is disclosed in this prior art.